Trail runs...should I buy a camelbak?

If you are making sure you are hydrating well in the days immediately before your long run then you'll be fine without water at 10 miles. If it's really hot then it's probably worth taking a little.

As is sounds like you are keen to keep increasing your distance and you are on routes that don't have a handy shop to grab a bottle of water from, then you've got a couple options; water belt or backpack bladder.

I have both and I like them equally. I find pro's and con's of each.

The belt has a velcro fitting so it doesn't move around or bounce and 4 slots for the small contoured water bottles. It's very comfortable. However it can be fiddly to get the bottles back into the slots whilst on the move, particulalry when tired and several times I've dropped one and either kicked it or trod on it.

The bag is my choice for when I'm running in rural areas because it has more storage space for a phone and (ahem) emergency toilet supplies. It's really easy to sip from the tube. On the downside, your back gets hotter than it otherwise would and the noise of the water sloshing around gets bloody annoying. The one I have now has a chest strap and a waist strap. This makes for a much more secure fit than one I had before with no waist strap. I've only had 1 litre and 1.5 litre bladders. I'd imagine that more than that is heavy and uncomfortable. There are plenty of decent and much cheaper options than camelbak.

When I used to do long runs, for some reason I hated camelbaks and really anything that i had to wear on my back or around my waist. I would just carry a bottle of water with me, and switch from hand to hand. My running group thought I was weird, but for some reason I just preferred it.

yes, when I was training for my half marathon, it was vital to be able to carry that much water. They are a pain at first, but after a couple of adjustments they fit well

I do not do trail running, but I do hike quite a bit. I personally would not go into the wilderness without water... not even 2 miles. The last hike I went on was in August (I've been pretty busy lately) for 12 miles. It was hot and humid... I had a 3L bladder that was almost gone at the half-way point (at a lake beach) so I refilled. Granted, there was a lot more time at hiking speeds vs. running speeds. And I sometimes tend to drink more water than others. Still, I can't imagine going out without any water at all.

Edit: Also, the bite tubes are quite convenient compared with a bottle, IMHO. You can see the tubing in my profile pic, and I have loops in the straps on my backpack so it doesn't flop around. I can just grab the end of the tube, raise it up to my mouth, bite down to release water, and drink. I have an insulated tube with a cap (that is attached) for when it is cold outside (to avoid freezing the water in the tubing).

I use a Salomon vest that uses two 17 oz soft flasks that are kept in front pockets. The pack can also accommodate a bladder in the back for those times I need more water but so far I haven't needed to use it. I've gone through the gamut of various hydration packs and so far the Salomon has been my go to both in training and during my trail races.

I'm not a runner, but I recently got one for long bike rides since my new bike doesn'thave water holders. I got the Nathan brand (cheaper than Camel Bak and more comfortable) and it worked great.

Try it out. You might like it. I used something similar for much of my summer running. Just make sure it's secured and tight or you will get chafed. And even if it is, after you start reaching a certain mileage, it might chafe still unless you lubricate.

Call me paranoid but esp since cell reception isn't great, I'd also carry bear spray/whistle/alarm or some other kind of self defense? I used to run with a super-loud alarm thing. Doesn't sound like the safest places to be running alone.

If you do out-and-back runs, take two half-size bottles. Stash one at the half way out point (1/4 distance) and go on with the other. Collect the stashed one on the way back.

So here is my poor man's method: I do long runs on Saturday mornings. The night before, I drive my running route with my car and leave out sealed water bottles every 3 or 4 miles. Then next morning when I run, I find my bottle on my route, break the seal (so I know they haven't been tampered with), and drink. I leave them by the side of the road if there aren't any garbage cans nearby and drive back to pick them up after I'm finished with my run. Maybe a hassle but I hate carrying water with me when I'm running.